Found an article that is interesting and it seems it doesn't use the starter motor to restart, here is an extract
But there's another, even more advanced version of engine stop-start that you'll find in Peugeot and Citroen cars. The two French companies share parts and use the same system, which makes use of a so-called 'reversible' alternator and capacitors to store reclaimed energy.
The system was introduced to Peugeots by the first generation 308. The alternator can reverse its polarity, switching its function to become a generator and reclaiming energy that would otherwise be lost.
It stuffs the capacitors full of electricity that the alternator then piles back into the engine and restarts combustion in just 400 milliseconds. Once the engine is warm, the alternator takes care of all restarting duties. Like Mazda's system, the fuel savings are immediate when the engine cuts out.
Peugeot estimates that 15% of the time taken for a typical commute is spent stationary, and even includes a dedicated stop-start timer within its models' trip computers so that owners can see the benefit.
This is the article
http://home.bt.com/lifestyle/motoring/motoringfeatures/the-truth-about-stop-start-engines-11363870847326